Microparticles as biomarkers of lung injury in human broncho-alveolar lavage fluid

Microparticles (MPs), submicron cell-derived vesicles released from the plasma membrane of cells after stimulation or apoptosis, have been studied in the vascular compartment as biomarkers and cellular effectors. MPs were reported in the peripheral blood, in the sputum of patients with emphysema or cystic fibrosis. MPs expose phosphatidylserine (PhtdSer) and membrane antigens from the parental cell The aim of the study was to harvest MPs from broncho-alveolar lavage fluids (BALF) of 21 patients with different pulmonary insults and to characterize their cellular origin. After differential centrifugation, concentrations of MPs were measured using original functional multiwell assays. MPs were first captured onto insolubilized annexin-5 (total MPs) or onto specific antibodies directed against membrane antigens borne by MPs and testifying to their cell origin (CD104, CD66b, CD14, CD3, CD20). MPs were quantified, taking advantage of their Phtdser content using prothrombinase assay. Total MPs concentration varied from 1.4 to 20.4nMPhtdSer (mean±SD = 6.7±4.8). MPs were derived from epithelial cells (0.33±0.51nMPhtdSer) and leukocytes: neutrophils (0.9±2.89nMPhtdSer), macrophages (0.64±1.01nMPhtdSer), T-lymphocytes (0.05±0.11nMPhtdSer) and B-lymphocytes (0.12±0.27nMPhtdSer). The concentration of neutrophils in BALF was correlated with that of epithelial-MPs (r=0.52, p=0.02). Four patients with the highest values of total MPs (10nMPhtdSer) had pulmonary infectious diseases with a higher BALF neutrophilia and reduced cell viability. These preliminary results demonstrate the feasibility of the measurement of MPs in BALF and suggest that the pattern of the cell origin of MPs may vary with the lung injury.